About this app

Room-by-room radiator sizing. Watts and BTU/h output for any room, factoring volume, glazing, external walls, roof and floor exposure, and insulation standard. Calculation Heat output per room with adjustments for: • Room type (8 presets: bedroom, living room, bathroom, kitchen, hallway, office, conservatory, garage) • Internal volume • Window-to-floor ratio • Number of external walls (0–4) • What's above (loft, pitched roof, flat roof, heated space) • What's below (garage, unheated cellar, uninsulated floor, heated floor) • Insulation level: poor (older single-glazed) → average (modern build) → good → excellent (new-build, triple-glazed) • Mean water temperature - ΔT30, ΔT35, ΔT40, ΔT50, ΔT60 ΔT correction uses the standard panel-radiator exponent (n = 1.30) per EN 442 testing convention. A 5% safety margin is applied to avoid undersizing. Heat-pump systems Select ΔT35 or ΔT30 to spec radiators for low-temperature systems. Output is rescaled — a 1000W ΔT50-rated radiator delivers ~630W at ΔT35 — so you size to actual delivered heat, not nameplate. Output • Watts and BTU/h side-by-side • Metric or imperial dimensions • Whole-home heat-loss total • Share or export room specs as text For plumbers, heating engineers, and heat-pump installers sizing radiator schedules, and homeowners or landlords running their own jobs.

Latest release

What’s New

Version 1.5 May 15, 2026

Thank you for using Radiator Calculator PRO. We’re always improving the app with performance enhancements, bug fixes, and tweaks to make the experience even better for you.

Audience growth

Ratings growth

Steady

7-day gain +0

Ratings / day 0.0

30-day gain +0

US rating-count history

0 ratings

Baseline captured. Growth appears after the crawler observes a changed rating count.

Momentum comes from crawler snapshots for the tracked storefront. “Viral growth signal” means unusually fast recent rating gains; it is an indicator, not download data.

Price tracking